Various types of structures are useful to disassociate selected substances from moving streams of fluid, gaseous or liquid, by which they are being carried. Filters and catalytic converters are examples of such devices and illustrate some in the wide range of structures and functions comprehended by the broad category into which such devices fall, and toward which the present invention is directed. Within that field, filters, for example, may be used to treat exhaust discharges which come from furnaces, internal combustion engines, or other combustion sources, that contain substances in particulate form, which, if not separated from their associated fluid medium, are discharged into the atmosphere. The offensiveness and harmfulness of this are well known. Such substances may be in the form of liquids and/or solids suspended in a gas (generally classified as "aerosols") or in a liquid, and may be relatively small in size. Although the features of the present invention can be beneficial in many if not all substance separation applications, they can be particularly advantageous when applied to the fields of filters, catalytic converters, odor suppressors, toxic constituent removal devices, and the like.
Typically, such devices are housed in some kind of chamber, which optionally may be a closed container through which the fluid that is to be processed is passed. Having entered a filter element, for example, the fluid stream is caused to pass through filtration medium before exiting the filter, by which solid and/or liquid particles being carried by the fluid are retained. Retention may be by entrapment mechanically by the filtration medium of the particles that are filtered out. In that case, the size of the material filtered out will be a function of the size of the pores or passageways through which the fluid can pass. With some filtrates, processing principles other than mechanical entrapment may be utilized. For example, some aerosols, such as the exhaust from a diesel engine, include comparatively large amounts of fine, particulate matter, liquid as well as solid, in suspension. Such suspended matter tends to stick to surfaces with which it comes into contact. Thus, filters for such applications, in addition or alternatively to mechanical entrapment, may be made capable of retaining desired substances from the fluid stream by providing contact surfaces to which such substances may adhere and by enhancing accessibility of those surfaces to the fluid.
The separation,, of desired substances from very hot fluids, particularly those bearing a proportionally high fraction of fine matter, can also impose limitations on the physical properties of the separation materials. There have also been various attempts to produce suitable devices which may be cleaned for reuse so as to extend their useful life, for example, by combustion of materials they have entrapped. This usually occurs at temperatures which are much higher than those encountered by the device in operation. Constituent materials that are suitable for such thermal environments may be difficult to form and retain in a shape or configuration that renders them capable of performing their desired separation functions. Thus, ceramic materials, while desirable in some circumstances because of their heat and chemical tolerance, present limitations as to how they may be formed into separation bodies. While they are susceptible to being formed into monolithic, solid bodies, they are inherently brittle and otherwise liable to break or deteriorate under physical stresses of the type regularly encountered in use. Other factors, such as the necessity to machine or die form in order to produce desired shapes, add to these objections. Some materials, such as ceramic fibrous yarns or felt-like sheets, are tolerant thermally of the range of temperatures encountered in such applications and are capable of being formed more easily into desired shapes.
Similar limitations also apply with respect to separation devices that are used in other treatments of fluid carrier media. For example, a catalytic converter typically may be exposed to a stream of hot gas or other fluid, as may also devices for deodorizing fluids. Such devices may utilize material, such as activated charcoal, to present chemically active surfaces as means for effectuating the desired separation process. Even though some such applications do not always expose the devices to very high temperatures, high efficiency and volume capability, with assurance that virtually all of the material passing through the device will be effectively treated, are desired characteristics which they have in common with devices of the type hereinbefore described, and therefore they present many of the same problems.
Accordingly, it is an object of this invention to produce fluid treatment devices that are capable of removing desired substances from suspension in fluids, liquid as well as gaseous.
Still another object of this invention is to produce such devices that are tolerant of comparatively high temperatures.
Yet another object of this invention is to produce such devices capable of achieve one or more of the foregoing objectives that may be more easily formed into desired shapes.
A further object of this invention is to produce such devices capable of achieving one or more of the foregoing objectives having a high flow-through volume capability.
Another object of this invention is to produce such devices capable of achieving one or more of the foregoing objectives that exhibit structural stability and durability in a wide variety of environments.
Still another object of this invention is to produce such devices capable of achieving one or more of the foregoing objectives which are susceptible to having retained material removed from it by incineration or other purging means.